1. Field of the Invention
This invention relates to apparatus for controlling odometers and speedometers. More particularly, this invention relates to odometers and speedometers which are driven by electrical pulses and may be adjusted for various conditions which affect indicated distances and speeds of a vehicle.
2. Technical Considerations and Prior Art
Frequently, it is desirable to obtain precise distance and speed measurements. For example, in the trucking industry, accurate distance measurements are needed to determine hauled ton/distance data. Frequently, obtaining accurate distance and speed data is frustrated because trucks may, from time to time, use different size tires.
It is readily seen that over the great distances that trucks now travel, a slight variation in tire size can result in considerable inaccuracy in measuring the actual distance covered. In addition, a variation in tire size makes it difficult for a driver to maintain a desired speed. If the tires are smaller than the norm for which the speedometer of the vehicle is programmed, then more miles than actually covered are recorded while the speed of the vehicle registers higher than it actually is. This means that customers can be overcharged for distance and that the truck may actually be moving slower than desired. In addition, the vehicle may receive periodic maintenance earlier than necessary and thus, the expense of maintaining the vehicle may be increased. On the other hand, if the tires are larger than necessary, it is likely that customers will be undercharged for actual mileage driven and that the vehicles will tend to travel at slightly excessive speeds. In addition, the vehicles will tend to exceed their maintenance periods and therefore, wear out earlier. Furthermore, if the vehicles travel at excessive speeds for long periods of time, then they will burn additional fuel. Essentially, since the vehicles, such as trucks, cover great distances, it is necessary that the operators have an accurate measure of the actual usage to which the vehicles are put.
Prior art awareness of this problem is exemplified by U.S. Pat. Nos. 3,865,305 to Sampey; 3,748,580 to Stevens; and 3,739,270 to Miller et al. However, in Sampey, calibration is manual and there is no speedometer function. In Stevens, the function of a speedometer is included with a manually set, measured-mile type of calibrate mode and in Miller et al calibration is accomplished by interchangeable plug-in modules. The following patents are also cited as being of interest with respect to prior art: U.S. Pat. Nos. 3,991,368 -- Powell; 3,947,664 -- Cox et al; 3,916,174 -- Moule; 3,868,570 -- Kopera, Jr.; 3,846,701 -- Sampey; 3,824,694 -- Lesperance et al; 3,614,617 -- Blake, Jr.; 3,446,947 -- Overstreet, Jr.; 3,396,333 -- Hin Hung Ho et al; 3,739,270 -- Miller et al.
In view of the foregoing considerations, there is need for a programmable odometer and speedometer which, among other things, will be of assistance to the trucking industry to help in properly determining distance and speed measurements. Furthermore, this need extends to analogous situations where there is need for accurate distance and speed measurement.